High silica crystalline zeolites and processes for their preparation

ABSTRACT

CRYSTALLINE ALUMINOSILICATE ZEOLITES HAVING SILICA TO ALUMINA MOLE RATIOS SUBSTANTIALLY HIGHER THAN PRIOR ART ZEOLITES ARE PREPARED BY A PROCESS WHEREIN A CONVENTIONAL CRYATALLINE ALUMINOSILICATE ZEOLITE IS CONTACTED WITH WATER AT AN ELEVATED TEMPERATURE AND THEN TREATED TO REMOVE ALUMINA FROM THE CRYSTAL LATTICE. THE WATER TREATMENT CAN BE ACCOMPLISHED BY CONTACTING THE CRYSTALLINE ALUMINOSILICATE ZEOLITE WITH A GAS CONTAINING AT LEAST 2% WATER AT A TEMPERATURE BETWEEN 800 AND 1500*F. HIGHER CONCENTRATIONS OF WATER ARE PREFERRED, AND, IN A PREFERRED EMBODIMENT, THE WATER TREATMENT IS ACCOMPLISHED IN TWO STEPS; VIZ, BY AFIRST TREATING THE CRYSTALLINE ZEOLITE WITH A GAS CONTAINING AT LEAST 2% WATER, FOLLOWED BY TREATMENT WITH PURE STEAM. FOLLOWING THE WATER TREATMENT, AMOPHOUS ALUMINA MAY BE REMOVED FROM THE ZEOLITE MATERIAL BY CONTACTING WITH A DILUTE MINERAL ACID OR AN ORGANIC ACID CHELATING AGENT.

July 6, 1971 P. E. EBERLY. JR., ETAL 3,591,488

HIGH SILICA CRYSTALLINE ZEOLITES AND PROCESSES Filed June 11, 1969 FORTHEIR PREPARATION ll Sheets-Sheet 1 FIGURE l INFRARED SPECTRA OF[(NH IN0 ]Y AFTER VARIOUS CALCINATION PROCEDURES TRANSMISSION RUN NO. SAMPLEDESCRIPTION TEMP. F.

47C I89 MG./CM. DISK AFTER 800 EVAC. AT 800F 740 I25 MG./CM. DISK AFTER800 WET AIR CALCINATION AT IOOOF. I68 I6.4 MG./CM. DISK AFTER BOO WETCALCINATION STEAMING AT I200F.

Run No. I68

Run No. 476 I0 I 3e40 O I I lw l f I I I 3900 3000 3700 3600 3500 34003300 32700 3I00 FREQUENCY, cMf' Pau/ Earl Eber/y, Jr Sebasllan MarcLaure/II Harry Edw/n Robson PAH NI III IUIIN! Y Filed June 11, 1969TRANSMISSION P. E. EBERLY, JR., ETAL 3,591,488 HIGH SILICA CRYSTALLINEZEOLITES AND PROCESSES FOR THEIR PREPARATION l1 Sheets-Sheet 2 FIGURE 2INFRARED SPECTRUM OF NH FAUJASITE RUN NO.

SAMPLE DESCRIPTION BNHLQQQZNOOIQSJY m KBr IOIO l l l l w 1000 900 800100 FREQUENCY, CM."|

Pau/ Ear/ [beer/y, Jr Sebasf/on Marc L aura/1! Harry E dw/n Robson rif'j,

IIIN NI Ill ION/V Y y 6,1971 P. E. EBERLY, JR.. ETAL 3,591, 88

HIGH SILICA CRYSTALLINE ZEOLITES AND PROCESSES FOR THEIR PREPARATIONFiled June 11. 1969 ll Sheets-Sheet 3 NOISSIWSNVHL Pau/ Ear/ Eber/y, JrSebastian Marc Lauren/ MI vn mns Harry Edwm Robson FATE! AII'ORNEY y 6,1971 p. E. EBERLY, JR., ETAL 3,591,488

HIGH SILICA CRYSTALLINE ZEOLITES AND PROCESSES FOR THEIR PREPARATIONFiled June 11, 1969 ll Sheets-Sheet 4 FIGURE 4 CALCULATED EFFECT OF Si0/A| O RATIO ON um'r CELL SIZE sI-o BOND IsIZ sI no Al O Al-O BOND LTOA Oo I I I I I I I I 9 0.2 x 0.4 T a (2)=UniI Cell Size AI SIO /Al 0RcIIio= 2 o A 0.6- ,L 9', 0 =UniI Cell Size At Any SiO /A| O Ratio 91 o0.8-

DO U LO"- II n L2 '2. L4" 3 w Ie--- o t [.8 5 20- 5 2.2- g 4 2.4- E 82.e--- o 2.a- 30 l l I l l l I l l I O I 4 B l2 I6 20 24 28 32 36 4O 44sIo /AI o Is/AI MOLAR RATIO Pau/ Earl Eber/y, Jr Saws/Ian Marc Lauren!Harry Edwin Robson PAIENI ATIOIi/VEY y 6, 1971 P. E. EBERLY, JR., ETAL3,591,488

HIGH SILICA CRYSTALLINE ZEOLITES AND PROCESSES FOR THEIR PREPARATIONFiled June 11, 1969 11 Sheets-Sheet 5 FIGURE 5 INFRARED SPECTRA OF ACIDFAUJASITES RUN NO. SAMPLE DESCRIPTION TEMP, F.

47C I89 MGJCM. DISK OF 800 [(NH4IQ QZNOO O8]Y AFTER EVAC. AT 800E 778I26 MG/CM. DISK 0F 800 4 012 028] Y AFTER STEAMING AT I200 F.

I I I I I I FREQUENCY, cIIII.

Paul Earl E bar/y, Jr Sebasfian Marc Lauren! Ml e Hons Harry EdwinRobson P475!!! AI'IOFNEY July 6, 1971 P. E. EBERLY, JR.. ETAI- 3,591,

' HIGH SILICA CRYSTALLINE ZEOLITES AND PROCESSES FOR THEIR PREPARATIONFiled June 11, 1969 11 Sheets-Sheet 6 FIGURE 6 INFRARED SPECTRA OF ACIDFAUJASITES RUN NO SAMPLE DESCRIPTION TEMP, F

470 I89 MG/CMZ DISK OF [(nng uu h e00 AFTER EVAC. AT 800F.

715 I25 MIG/cm? DISK OF [(NH N 1 ]Y e00 AFTER STEAMING AT I200 F.

I I I I Run No. 778

% TRANSMISSION Run No. 470

l I I I 2100 2000 I900 I800 I700 I600 I500 I400 I300 I200 FREQUENCY,cMf' Paul Ear/ E bar/y, Jr Sebastian Marc Laurent I/vvewwfls Harry EdwinRobson PAIENI' A! OWN! Y y 1971 P. E. EBERLY, JR.. ETA!- 3,591,

HIGH SILICA CRYSTALLINE ZEQLITES AND PROCESSES FOR THEIR PREPARATIONFiled June 11, 1969 11 Sheets-Sheet 7 FIGURE 7 INFRARED SPECTRA OF ACIDFAUJASITES AFTER STEAMING TRANSMISSION l I J L I300 I200 H00 1000 900800 100 e00 500 400 FREQUENCY, cMf' Paul Ear/ Eber/y, Jr Sebastian MarcLaure/1f mfl Harry Edwin Robson I" PATENT ATNJRNEY July 6, 1971 p, L JR"ETAL 3,591,488

HIGH SILICA CRYSTALLINE ZEOLITES AND PROCESSES FOR THEIR PREPARATIONFiled June 11, 1969 ll Sheets-Sheet 8 FIGURE 8 INFRARED SPECTRA OF ACIDERIONITES AT 800F.

I I I l I I l CALCINED UNDER VACUUM STEAMED AT l200F.

Run N0. 64d Run No. I89A FREQUENCY, CM."

* A=OPT|CAL ABSORBANCE/GRAM Paul Ear/ Eber/y, Jr SebasI/an Marc LaurentvE v rons Harry Edw/h Robson Fifi/VI AVIOIV/VL'Y July 6, 1971 Filed Junel1, 1969 TRANSMISSION P. E. EBERLY, JR.. ETAL 3,591,488 HIGH SILICACRYSTALLINE ZEOLITES AND PROCESSES FOR THEIR PREPARATION 11 Sheets-Sheet9 FIGURE 9 INFRARED SPECTRA OF ACID ERIONITE S RUN NO. SAMPLEDESCRIPTION I09 NH -ERIONITE (BEFORE STEAMINGI IN KBr I88 NH -ERIONITE(AFTER STEAMING) IN KBr I I I I I IOQO 900 800 700 FREQUENCY, cm?

Pau/ Earl Eber/y, Jr Sebastian Marc Laurent Harry Edwin Robson PATENTATTORNEY INVENTU/IS July 6, 1971 Filed June 1.1, 1969 TRANSMISSION P. E.EBERLY, JR, ETAL 3,591,488 HIGH SILICA CRYSTALLINE ZEOLITES ANDPROCESSES FOR THEIR PREPARATION l1 Sheets-Sheet 10 FIGURE I0 INFRAREDSPECTRA OF ACID MORDENITE AT 800F.

RUN NO. SAMPLE DESCRIPTION I94A I5.I MG./CM.2 DISK I98A |s.| MG./CM.2DISK I I I I I I I I BEFORE STEAMING AFTER STEAMING AT I200F Run No.I94A Run No. I98A I I L I I I I I 3800 3700 3600 3500 3900 3800 37003600 3500 FREQUENCY, cm." A=0PTICAL ABSORBANCE/GRAM Paul Ear/ Eber/y,Jr. .Sebas/mn Marc Laurent Harry Edwin Robson P475! ATTORNEY INVENTORSJuly 6, 1971 P. E. EBERLY, JR., ETAL 3,591,488

HIGH SILICA CRYSTALLINE ZEOLITES AND PROCESSES FOR THEIR PREPARATIONFiled June 11, 1969 ll Sheets-Sheet 11 mm INFRARED SPECTRA OF ACIDMORDENITE RUN N0. SAMPLE DESCRIPTION I92 ACID MORDENITE (BEFORESTEAMING) IN KBr I96 ACID MORDENITE (AFTER STEAMING AT I200F) IN KB:

I I I 'I I I I I l l A I I I I I I H 60% I J I H TRANSMISSION I 0 I400I300 I200 I IOO I000 900 800 700 600 500 400 FREQUENCY, 0M."

Paul Ear/ E ber/y, Jr Sebastian Marc Laurent MEM s Harry Edwin RobsonPAICN! nr/onm. r

United States Patent 3,591,488 HEGH SILICA CRYSTALLINE ZEOLETES ANDPROCESSES FOR THEIR PREPARATION Paul Earl Eberiy, Jr., Baton Rouge,Sebastian Marc Laurent, Greenwell Springs, and Harry Edwin Robson, BatonRouge, La., assignors to Esso Research and Engineering CompanyContinuation-impart of application Ser. No. 552,911, May 25, 1966, Thisapplication June 11, 1969, Ser. No. 832,109

U.S. Cl. 208-111 Int. Cl. Cltlg 13/02 Claims ABSTRACT OF THE DISCLOSUREwith the disclosure, pure steam may be used. In a preferred embodiment,the water treatment is accomplished in two steps; viz, by first treatingthe crystalline zeolite with a gas containing at 1east2% water, followedby treatment with pure steam. Following the water treatment, amorphousalumina may be removed from the zeolite material by contacting with adilute mineral acid or an organic acid chelating agent.

CROSS-REFERENCE TO RELATED APPLICATION This application is acontinuation-in-part of copending application Ser. No. 552,911, filedMay 25, 1966, Pat. No. 3,506,400.

BACKGROUND OF THE INVENTION Field of the invention The present inventionrelates to new compositions of matter consisting of crystallinealuminosilicate zeolites of the molecular sieve type having silica toalumina mole ratios very substantially higher than has heretofore beenobtainable for use in hydrocarbon conversion reactions. Morespecifically, the present invention involves a process wherebycrystalline aluminosilicate zeolites of the molecular sieve type aresubjected to a heat treatment in the critical presence of water toeffectuate removal of a substantial portion of alumina from the zeolitecrystal structure thereby resulting in a high silica content crystallinezeolite molecular sieve. In a further embodiment of the presentinvention, the amorphous alumina produced by the heat treatment in thepresence of water is removed from the crystalline zeolite structure bymeans of extraction with a leaching or complexing agent selective toalumina.

Description of the prior art Crystalline aluminosilicate zeolites,commonly referred to as molecular sieves, are now well known in the art.They are characterized by their highly ordered crystalline 3,591,488Patented July 6, 1971 structure and uniformly dimensioned pores, and aredistinguishable from each other on the basis of composition, crystalstructure, adsorption properties, and the like. The term molecular sieveis derived from the ability of the zeolite materials to selectivelyadsorb molecules on the basis of the molecular size and form. Thevarious types of molecular sieves may be classified according to thesize of the molecules which will be rejected (i.e., not adsorbed) by aparticular sieve. A number of these zeolite materials are described, forexample, in US. Pats. 3,013,982-86 wherein they are characterized bytheir composition and X-ray diffraction characteristics. In addition totheir extensive use as adsorbents for hydrocarbon separation processesand the like, it has recently been found that crystallinealuminosilicate zeolites, particularly after cation exchange to reducealkali metal oxide content, are valuable catalytic materials for variousprocesses, particularly hydrocarbon conversion processes.

In general, the chemical formula of anhydrous crystallinealuminosilicate zeolites expressed in terms of moles may be generallyrepresented as:

wherein M is a metal cation, generally sodium or potassium as foundinthe natural form or when synthesized; n is the valence of the metalcation; and X is a numher from about 1.5 to about 12, said value beingdependent upon the particular type of zeolite. Included among thewell-known natural zeolites are mordenite, faujasite, chabazite,gmelinite, analcite, erionite, etc. Such zeolites differ in structure,composition and particularly in the ratio of silica to alumina containedin the crystal lattice structure. Similarly, the various types ofsynthetic crystalline zeolites, e.g., synthetic faujasite, mordenite,zeolite Y, etc., will also have varying silica to alumina ratiosdepending upon such variables as composition of the crystallizationmixture, reaction conditions, etc.

It has been found that for general catalytic or adsorptive uses, thealuminosilicate zeolites having higher silica to alumina ratios will bepreferred due to their higher stability. Generally speaking, the higherthe silica-alumina ratio in an aluminosilicate, the greater thestability to heat, steam and acid. This is true not only betweendifferent crystalline types of zeolites, e.g., mordenite having a silicato alumina mole ratio in the range between 8/1 to 12/1 generallyexhibits better stability to acid than faujasite having a silica toalumina mole ratio in the range between 3/1 to 6/ 1, but additionally incompositions of the same crystalline type such as for example, afaujasite having a silica to alumina mole ratio of about 6/1 generallyexhibits greater steam stability than a faujasite having a silica toalumina mole ratio of about 3.5/1. Loss of stability in crystallinealuminosilicate zeolites of the molecular sieve type is generallyexhibited by a lowering of the order of crystallinity of the material.Such reduction in the degree of crystallinity in an aluminosilicatezeolite molecular sieve will in turn adversely affect the desirablecharacteristics of catalytic activity or adsorp tivityof such materials.It is obvious, therefore, that any process which would enhance acrystalline aluminosilicate zeolite molecular sieves resistance todegradation of crystallinity or which would form a molecular sieve of ahigher order of crystallinity than was previously obtainable would behighly desirable.

In synthetic crystalline aluminosilicate zeolite molecular sieves, thesilica/alumina mole ratio is essentially determined by the nature of thestarting materials and the relative quantities of such materials used inthe preparation of the zeolite. Some variation in the silica/aluminaratio can be obtained by changing the proportion of reactants, i.e.,increasing the relative concentration of the silica precursor relativeto the alumina precursor. However, definite limits in the maximumobtainable silica/alumina mole ratio are observed. For example,synthetic faujasites having a silica to alumina mole ratio of about 5.2to 5.6 can be obtained by increasing the relative proportion of silicaprecursor. However, when the silica proportion is in creased to'evenhigher levels no commensurate increase in the silica to alumina moleratio of the crystallized synthetic faujasite is observed. Thus, thesilica to alumina mole ratio of about 5.65 must be considered an upperlimit in a preparative process using conventional reagents.Corresponding upper limits in the silica to alumina mole ratio ofmordenite and erionite via the synthetic pathway are also observed.

The art has suggested possible methods of increasing the silica toalumina mole ratios of crystalline aluminosilicate zeolite molecularsieves beyond either the synthetic upper limits or that of the naturallyoccurring material. One procedure disclosed in South African Pat. No.64/472, granted Feb. 3, 1964, to Kerr et al., teaches a process for theselective complexing of alumina from crystalline aluminosilicatezeolites by using a chelating agent such as di(tetraethyl ammonium)dihydrogen ethylene diamine tetraacetic acid or acetate. The acidicchelating agent is utilized both as a medium for providing cationexchange to yield the hydrogen form of the crystalline aluminosilicatezeolite and additionally as a means of removing alumina selectively toproduce a zeolite having a higher silica to alumina mole ratio.

A disclosure in a similar vein is to be found in South African Pat. No.65/922, published Feb. 22, 1965, to British Petroleum Company, whichpatent indicates that mordenite treated with a mineral acid will loseabout one atom of aluminum per unit cell of the mordenite crystallattice. This lost aluminum is believed to be replaced by four hydroxylgroups.

The above methods for increasing the silica to alumina mole ratio incrystalline aluminosilicate zeolites are considered disadvantageous. Forexample, use of an acid medium to extract or chelate alumina out ofcrystalline zeolites is generally contraindicated for those zeoliteshaving initial silica to alumina mole ratios less than about 7.0. Suchzeolites generally are structurally unstable in the presence of acid andwill suffer a large degree of crystal degradation when exposed thereto.Thus, the prior art techniques would generally find applicability onlyin crystalline zeolites having initially high silica to alumina moleratios, such as in mordenite. If a crystalline zeolite is utilizedhaving a lower silica to alumina mole ratio, it is necessary to employcareful pH control in order to utilize the cherating or acid extractionprocedures described above. Such control adds to the expense and reducesthe overall etficiency of such a process.

SUMMARY OF THE INVENTION It is, therefore, an object of the presentinvention to provide a process for the selective removal of alumina fromthe tetrahedral sites in the crystal lattice of aluminosilicate zeolitemolecular sieves. It is a further object of the present invention toprovide a process which will increase the silica to alumina mole ratioin crystalline aluminosilicate zeolites to levels unattainable bysynthesis or unavailable in the natural material. It is a still furtherobject of the present invention to provide such processes which willoperate in such a manner as to retain a high level of crystallinity inthe resulting aluminosilicate zeolite so as to not adversely effect thedesirable catalytic and adsorptive properties of these materials. Yetanother object of the present invention is to provide crystallinealuminosilicate zeolite molecular sieves having substantially enhancedstructural stability over those available by practice of currenttechniques of preparation. A still further object of the presentinvention is to provide a process for effectively removing virtually allof the alumina tetrahedra in a crystalline aluminosilicate to form as anew composition of matter a pure polysilicate crystalline material whichessentially retains the crystal structure of the starting crystallinealuminosilicate. Such crystalline polysilicates having essentially thecrystal structure of a molecular sieve are of great interest incatalytic reactions wherein this catalytic activity is not adverselyaffected by the presence of metal cations since such metal cations arenot required in the polysilicate crystal lattice to achieve electricalneutrality.

The essence of the present invention is based upon the discovery thataluminum can be selectively abstracted from the tetrahedral sites in acrystalline aluminosilicate zeolite molecular sieve by heat treating thezeolite for a period of from about 1 to 24 hours, preferably 4 to 16hours, in the critical presence of water at temperatures in the range ofabout 800 to 1500 F., preferably 1000 to 1200 F. It is generally desiredthat at least 2% water be present in the treating gas, preferably atleast 5%, and most preferably 25%. In a preferred embodiment of thepresent invention, the acidic, e.g., hydrogen or hydro gen precursor,such as ammonium, form of a crystalline aluminosilicate zeolite istreated with steam for a period of from about 4 to 24 hours, preferably16 to 24 hours, at a temperature in the range of about 1000 to 1200 F.,and a pressure of at least 10 p.s.i.a. to effectuate selective removalof alumina from the crystal lattice. In one embodiment, the zeolite isfirst wet air calcined at a temperature in the range of about 650 to1200 F. and then is subjected to steaming as before. The alumina soproduced is in an amorphous form and remains within the gross structureof the zeolite. This amorphous alumina may be removed from the zeolitematerial by appropriate treatment with a dilute mineral acid or anorganic acid chelating agent. An unobvious benefit is obtained byutilizing the process steps of the present invention in the orderdescribed. For example, by following the process steps of the presentinvention it is possible to preserve the structural stability andcrystallinity of zeolites having relatively low initial silica toalumina mole ratios which zeolites would otherwise be damaged by directtreatment with an acid medium or chelating agent.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a graph of the infraredspectra of ammonium forms of faujasite after various calcinationprocedures of the present invention.

FIG. 2 contains a graph of the infrared spectrum of ammonium faujasiteafter vacuum calcination.

FIG. 3 contains a graph of the infrared spectrum of ammonium faujasiteafter wet air calcination at 1000 F.

FIG. 4 contains a graph of the effect of silica to alumina mole ratioson the unit cell size of the zeolite.

FIGS. 5-7 contain graphs of the infrared spectra of ammonium faujasitesafter steaming.

FIG. 8 contains a graph of the infrared spectra of acid erionites aftercalcination and steaming.

FIG. 9 contains a graph of the infrared spectra of acid erionites aftersteaming.

DESCRIPTION OF THE PREFERRED EMBODIMENTS By the utilization of the steamtreatment procedure of the present invention from 0 up to about 98% ormore of the original alumina present in the crystalline aluminosilicatesmay be abstracted, thus producing molecular sieves which have silica toalumina mole ratios which are increased substantially above theirinitial values. More particularly, by treatment with the process of thepresent invention crystalline aluminosilicates having initial silica toalumina mole ratios greater than 3-5 are converted into zeolites havingsilica to alumina mole ratios greater than about 5-10 depending on thenature of the zeolite, preferably greater than about 20, and still morepreferably greater than about 50.

The acid zeolites utilized in the practice of the present process aregenerally obtained by cation exchanging zeolites which are initially inthe alkali metal form with ammonium ions (generally as the ammonium saltin aqueous media) by means of any conventional cation exchangetechnique. For purposes of this invention, it is generally desired thatmore than 50% and preferably more than 75% of the original metal cationsbe exchanged with ammonium ion. The ammonium form is subsequently heatedto a temperature in the range from about 600 to 1000 F. to produce theacid zeolite.

In addition, it has been found that, subsequent to the heat treatmentprocedure of the present invention, zeolites useful as catalysts invarious hydrocarbon conversion reactions, such as cracking,hydrocracking, isomerization, hydroisomerization, alkylation,hydrogenation, dehydrogenation, olefin dimerization or polymerizationmay be prepared by base exchanging the steamed zeolite with cations suchas ammonium ion, and/ or metal ions selected from the following groupsof the Periodic Table: Groups II-A, I-B to VIIB, VIII, and the rareearth ions with atomic numbers 57 to 71, such as the following metalions: Mg, Ca, Sr, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru,Rh, Pd, Ag, Cd, the lanthanides, Hf, Ta, W, Re, Os, Ir, Pt, Au, and Hg,preferably those ions in Groups II-A, VIII and the rare earths. It hasbeen discovered that, by the use of such a procedure, nearly all thealkali metal cations which were still present prior to the present steamtreatment, may be removed. Thus, a final zeolite product may be obtainedhaving an alkali metal content below about 0.5 wt. percent, preferablybelow about 0.2 wt. percent.

Where this final cation exchange procedure consists of exchange withammonium ions, the ammonium form is subsequently heated to a temperaturein the range from about 400 to 1500" F. to liberate ammonia gas andproduce the acid or hydrogen form of the zeolite.

Additionally, it has been found that improved catalysts forhydrocracking reactions may be obtained by impregnation of from 0.1 towt. percent, preferably 0.1 to 2 wt. percent of a hydrogenationcomponent on the crystalline aluminosilicate zeolite subsequent to thesteam treat ment and/or base exchange procedure of the presentinvention. It is critical though, that this impregnation occurssubsequent to the steam treatment procedure of the present invention. Inthis manner, a hydrocracking catalyst of unusual activity andselectivity may be obtained. The hydrogenation component so utilized maybe selected from Groups IIB to VIIB and VIII of the Periodic Table,particularly Groups VI-B, VII-B, VIII, and most particularly Group VIII.A variety of compounds of these elements may be used for impregnation.For example, the nitrates, chlorides and other halides, sulfates,aminohalo compounds, carbonyls, cyanides, oxides, sulfides, acetates,carbonates, and the like. Also, compounds containing the metallicelement in the anion such as H PtCl H PdCl HReO H WO H CrO etc. Thislist is not intended to be exclusive and other compounds containingthese elements can be used for impregnation. Subsequent to impregnation,the material is calcined at elevated temperatures and reduced withhydrogen to activate the catalyst for hydro-reactions. Depending on thenature of the element, various states of reduction of the hydrogenationcomponent may be realized ranging from the pure metal up to the originaloxidation state.

In the original heat treatment of the ammonium zeolite, it has beenfound that the structure of the heat treated product as well as itsstability depend, to a large extent, on the method of calcination. Time,temperature and Water content of the calcining gas all play an importantpart in this respect. The effect of these variables in the preparationof a zeolite Y having an extremely high silica to alumina mole ratio,e.g., 15 to 1 or greater, is indicated in the following discussion.

The ammonium form of a synthetic faujasite (NH Y) prepared by ammoniumion exchange of sodium faujasite was heat treated at varioustemperatures and in the presence or absence of water. It was found thatheat treatment in dry air (dew point of F.) gave the same results asheat treatment in vacuum. Under either of these aforementionedconditions, ammonia gas is liberated from the solid leaving behindprotons in well-defined hydroxyl groups. These protons satisfy theoriginal charge requirements of the structure and the material can beproperly called hydrogen-faujasite.

Infrared spectrum of NH Y after calcination under vacuum at 800 F. isshown by the bottom curve of FIG. 1. The OH groups are characterized byinfrared bands at 3740, 3640 and 3550 cm. The groups at 3740 cm.- havealso been observed with silica gel and amorphous silica-alumina catalystand are not believed to be necessarily characteristic of faujasite. Thetwo remaining intense bands, however, have not been observed on othersolids and are only seen in the faujasite structure calcined in thismanner. The hydroxyl groups at 3640 cm.- interact with adsorbedhydrocarbons and must be in the accessible cage positions. On the otherhand, those at 3550 cm.- do not interact with adsorbed hydrocarbons andare believed to be in the isolated bridge positions not accessible tothe hydrocarbons.

Vibrations of the crystal lattice are observed in the spectral regionbelow 2000 cm.- Spectra are shown in FIG. 2 and the bottom curve of FIG.6 for the vacuum calcined sample. The position of these bands depends onthe silica-alumina ratio of the faujasite. As the ratio increases, thebands shift to higher frequencies. See in this regard the work by W.Eitel, Silicate Science, volume I, pages 2043, Academic Press, New York,1964.

The structure obtained by heat treatment under vacuum or dry air is notvery stable. Crystallinity is gradually lost by further heating to 1200F. This loss in structure is accompanied by commensurate loss inhydroxyl groups. In addition, the material is quite sensitive torehydration. The structure can be destroyed by merely exposing thecalcined sample to the atmosphere Where water can be picked up at roomtemperature.

If NH Y is heat treated in wet air (containing about 3.2% H 0) at 1000F. for 16 hours, a product results which has a considerably lowerhydrogen content than that obtained by heat treatment in the absence ofwater. This is seen in FIG. 1 by an overall reduction in intensity ofthe infrared bands due to hydroxyl groups. The number of characteristicOH groups of faujasite at 3640 and 3550 cm.* has greatly decreased.There is however, some indication that the number of groups at 3740 cm?has increased. The reasons for this are not clear but could beassociated with the formation of a small amount of amorphous material.

Concomitant with the overall hydrogen loss, a shift in the infraredfrequencies of the crystal lattice vibrations has also occurred, as seenby comparing FIGS. 2 and 3. This shift to higher frequencies indicatesthat the silicaalumina ratio of the faujasite has increased as a resultof partial removal of alumina from the structure.

X-ray diffraction data on several samples before and after wet aircalcination are listed in Table I. The values for the X-raycrystallinities are obtained by averaging the peak intensity of a numberof diffraction lines. All the materials listed are considered to be wellcrystallized faujasites. The lower diffraction intensities of theK-containing forms can be accounted for by the higher X-ray absorptioncoefiicient of the potassium ions. In this table it is important to notethe decrease in unit cell size which occurs on wet calcination. Thisdecrease becomes more pronounced with increasing amount ofammonium-exchange and, moreover, is consistent with the theory thatalumina has been partially removed from the faujasite. The length of theSiO bond is shorter than that of the Al-O bond and consequently the cellsize is expected to decrease with increasing amounts of silica in thelattice. The calculated magnitude of this effect is shown in FIG. 4where the percent decrease in unit cell size is plotted as a function ofsilica-alumina ratio. Thus, with a 92% NH; faujasite the cell sizedecrease upon Wet calcination could mean an increase in thesilica-alumina ratio from 4.7 to about 6.0.

TABLE I.X-RAY CRYSTALLINITY AND UNIT CELL SIZES OF FAUJASI'IES AFTER WETAIR OALCINATION AT l,000 F.

After wet air calcina- Thus, both the infrared, as well as diffractiondata, indicate that alumina has been partially removed from thefaujasite by wet air calcination. This partial removal lowers the numberof protons needed to satisfy the negative electrical charges normallyassociated with alumina tetrahedra in the faujasite.

We turn now to the discussion of the structure obtained by a two-stepcalcination in which the material is first wet air calcined at 1000 F.for 16 hours and then steamed at 1200" F. and 1 atm. for an equal periodof time. This final steam treatment serves to complete the reactionsinitially observed in the wet air calcination.

In FIG. 1, the infrared spectrum of a 92%. NH Y sieve is shown afterhaving been steamed at 1200 F. and is compared with spectra obtained bythe other methods of calcination. The characteristic faujasite hydroxylgroup bands at 3640 and 3550 cm.- have been greatly reduced inintensity. Moreover, this loss of hydroxyl groups has occurred with verylittle loss in crystal structure since the material has a crystallinityvalue of 163% (see Table II). The band at 3740 CHI-"1, which could beassociated with amorphous material in the faujasite, has been onlyslightly affected by the steaming process.

crease in weight of the solid upon deuterium exchange. By thistechnique, the material was found to contain less than 10% of the numberof protons theoretically necessary to satisfy the charge requirements ofthe original structure.

This loss of hydrogen causes definite changes in the structure of thecrystal lattice as evidenced by shifts in the infrared latticevibrations. Spectra in the region from 2100 to 1200 cm:- are shown inFIG. 6. Although the bands in this region cannot be assigned to specificgroup vibrations, they are known to be overtones of crystal latticevibrations. In comparison to the vacuum calcined material, the steamedsample has very well defined bands in this region. These bands arefrequently observed on high silica content materials. Furthermore, thesebands occur at higher frequencies than their counterparts in the vacuumcalcined material. The latter only exist as weak and rather broad bands.

This shift in frequency of crystal lattice vibrations is more noticeablein the region below 1300 cmf Here, infrared spectra are best obtained byincorporating 1% of the sample in a matrix of KBr. Spectra of foursteamed acid faujasite samples are shown in FIG. 7. In comparing thesecurves with that obtained with the original material (FIG. 2), weobserve that every lattice vibration band has shifted to higherfrequencies upon steaming. The magnitude of these shifts is much largerthan that observed by wet air calcination alone (FIG. 3) and indicatesthat the silica/alumina ratio of the faujasite has been increased to acorrespondingly higher value.

Unit cell data, obtained by X-ray diffraction studies are given in TableII. These are all lower than those of the wet air calcined samples andare, within experimental error, values calculated for pure silicafaujasite.

If, as indicated in the above discussion, the effect of steaming is toremove alumina from the faujasite structure, we would expect the aluminathus formed to be more readily attacked by chelating agents than aluminain the faujasite structure itself. Several extractions were made byrefluxing with a tetraethyl ammonium hydroxide solution of ethylenediamine tetraacetic acid (EDTA) and the resulting data are given inTable III for both a fresh and steamed sample of NH Y.

TABLE IL-PROPERTIES OF FAU-TASITIES AFTER CALGINING IN WET Relative tothat of acid-faujasite prepared by vacuum calcination at 800 F.

Determined by deuterium exchange.

A more striking example of the effects of steaming is shown by theinfrared spectra in FIG. 5. The steam sample was prepared from a 72% NHY sieve having a relatively high silica/alumina mole ratio of 5.65. The-OH bands have almost disappeared. Detailed data on this sample aregiven in Table II. The X-ray crystallinity value was 185% and benzeneadsorption capacity was roughly of that of the original vacuum calcinedsample. This partial loss of capacity probably reflects the blocking ofsome of the pore structure by amorphous material. A more nearlyquantitative measure of the hydrogen content of the steamed material wasobtained by recording the in- TABLE IIL-RESULIS OF ETHYLENE DIAMINE'IETRA- ACETIC ACID (EDTA) EX'IRACTIONS ON [(NHDmmNaumlY Wet air at1.000 F.

*3.5 grams faujasite treated with a solution of 4.8 grams EJJTA in 71ml. N(Et) OlI plus 15 ml. I1 0 at refluxing temperature.

The results show that alumina is indeed more easily removed from thesteamed faujasite. After four extractions, the steamed material yieldeda faujasite having the extremely high silica/ alumina mole ratio ofabout 20. As indicated previously, it is extremely difficult by directsynthesis to make a faujasite with even a 6/1 silica to alumina moleratio.

The process of the present invention is also effective in increasing thesilica to alumina mole ratio in erionite. Erionite has rather poortransmission properties for infrared radiation, particularly in thehydroxyl group region. To obtain better spectra, the hydroxyl groupswere transformed into their corresponding deuterium analogs by exchangewith D at 800 F. Infrared spectra in the -OD region are shown in FIG. 8.In the vacuum calcined sample, a small peak appears at 2750 cm." whichis the -OD analog of the OH group at 3740 cmr This could be associatedwith a small amount of amorphous impurity in the zeolite. The intenseband at 2640 cm." represents the characteristic OD groups of erionite.After steaming, infrared absorption, as given by the absorbance (A)values, has greatly decreased in this characteristic region and twolower intensity bands can be resolved. At the present time, the exactsignificance of these two bands has not been fully established. Withthis loss of hydrogen upon steaming, the crystal lattice vibrations haveall shifted to higher frequencies, as seen in the spectra of FIG. 9. Inaddition, the X-ray diifraction lines now occur at larger angles,indicating a decrease in lattice spacings and consequently a smallerunit cell size.

Since all these physical data indicate that alumina has been removedfrom the lattice structure by steaming, extraction experiments were donewith hydrochloric acid in order to isolate high silica erionite. Theseresults are listed in Table IV. The steaming process has improvederionites 3 acid resistance as reflected by the 42% crystallinityremaining after a one normal HCl treatment. The silica/ alumina ratiowas observed to have increased to a value of 29/ 1.

TABLE IV.RESULTS OF HCl EXTRACTION* ON ERIONITE Sample Natural erioniteSynthetic acid erionite X-ray X-ray cryst., SIOQ/AIQOQ cryst.,SiO2/Alz03 percent ratio percent ratio Method of calcination Notcalcined Steamed at 1,200 F.

Initial 100 7. 3 108 6. 9 1 N HCl 8 42 2S).

*3 grams erionite treated with 30 ml. H01 solution for 16 hours atrefluxing temperature.

High silica erionite of low cation content can also be made fromammonium erionite by steaming followed by a more dilute acid treatment.Data are given below in Table V for a steamed acid erionite before andafter extraction with 0.1 N HCl.

TABLE V Alter extraction with 0.1 Initial N 1101 Chemical analysis, wt.percent:

N320 0.05 0.00 K20 3. 44 0. 96 SiOz. l 77. 57 92. 28 A1202. 18. 94 6. 76Sim/A1 0 ratio 6. 9 23. 0

quencies, as seen in FIG. 11. At the same time, the crystallographic dspacings have decreased, indicating a smaller unit cell. These facts,which are completely analogous to those of faujasite and erionite, provethat alumina has been removed from the structure by steaming.

It is, therefore, evident that the process of the present inventioninvolves the following procedural steps: (1) ion exchange of acrystalline aluminosilicate zeolite to prepare the H+ or NH; form; (2)heat treatment of the acid form of the zeolite in the critical presenceof water (preferably steam) at elevated temperatures, and may alsoinclude; (3) leaching of extraneous alumina from the product of (2) bytreating with dilute acid or some chelating agent selective for alumina.Step (2) may, of course, involve a two-part procedure wherein the acidmolecular sieve is treated with wet air at a moderately elevatedtemperature and is then treated with steam at a still more elevatedtemperature. It is also understood that the resulting product of theprocess would preferably undergo a drying and/or calcining procedureprior to its use as an adsorbent or catalyst.

It is also understood that prior to use as a catalyst, the followingsteps may be employed; (4) base exchange of nearly all of the remainingalkali metal content of the crystalline alumino-silicate subsequent tostep (2) above, utilizing cations selected from the group consisting ofammonium ions, and/or metal ions as previously listed in column 5, line26, e'tc.; and it may also include (5) impregnation of the thus steamedand treated zeolite with a hydrogenation component selected from GroupsII-B to VII-B and Group VIII of the Periodic Table, and including Ti, V,Cr, Mn, Fe, Co, Ni, Zn, Mo, Ru, Rh, Pd, Hf, Ta, W, Re, Os, Ir, Pt.

Although the description of the process so far involves the treatment ofthe zeolite component alone, it is to be understood that prior to theprocess, or at any stage therein, or subsequent to the process, thezeolite may be incorporated with a suitable matrix. For example, forengineering or other technical reasons, it is sometimes desirable toproduce a catalyst having only a minor percentage of zeolite and a majorpercentage of a high surface area, nonzeolitic matrix such as alumina,silica gel, amorphous aluminosilicate, alumina/boria, silica/ magnesia,and the like. The process described herein can be applied to thesematerials as well, with variations apparent to those skilled in the art.

The process of the present invention will be still more clearlyunderstood by reference to the following examples which are advanced forthe purposes of illustration only and should not be taken as limitingthe scope of the present invention in any way.

Example 1 This example demonstrates the critical nature of the heattreatment steps of the present invention. Sodium faujasites havingsilica to alumina mole ratios of from 5 to 6 were subjected to varyingdegrees of base exchange with ammonium ions. The resulting faujasiteswere then subjected to one or more of the following process stepsincluding calcination (in a muffle furnace with ambient air containingabout 2% H A), steaming at a pressure of about 1 atm., and acidextraction with a sulfonic acid type cation exchange resin; 6 cc. acidregenerated resin/ g. zeolite in water slurry at C. for 4 hours. Thequalitative effects of these process steps, taken singly or in variouscombinations, were determined by examination of the comparativecrystallinity and the unit cell size of the product. X-ray crystallinityis calculated by summing the observed amplitudes of the 10 strongestlines of the faujasite pattern in arbitrary scalar units subtractingbackground intensity and dividing this sum by the corresponding sum forthe laboratory standard known to be a good crystalline faujasite. Thequotient expressed as percent is reported as X-ray crystallinity; thelaboratory standard has been arbitrarily assigned a crystallinity of100%.

1 1 The results of these experiments are tabulated in Table VI givenbelow.

12 The higher activity of the treated catalyst indicated by higherw/hr./w for 60% conversion is believed due TABLE VI 5102/ N114 Acid ex-A1103 exch. Calciuation Steaming traction Cryst. An

Experiment:

5 6 None one 188 24. 71 5 6 l,000 F.l hours 82 24. 50 0 do 8 88 24.40 5(i 1,000 F.l6 hours- 56 24. 5 6 1,200 F.16 hours do 07 24. 5 6 .do do es00 24.28 5 0 None 800 F.-16 hours-.. None 02 24. 5 6 (1 Y 130 24. 44 5(i 128 24. 5 1 207 24. 67 5 6 120 24. 44 G 3 178 24. 61 6 3 do doYes...... 8 0 3 1,000 F.-16 hours... 1,200 F.16 hours... Yes 203 24. 375 6 None Yes 0 None Examination of the above data indicates thefollowing critical points. In the first place, it is clearly evidentthat acid extraction alone will destroy the crystallinity of thefaujasite sample, even one having as high an initial silica to aluminamole ratio as 6 to 1 (Experiments 11 and 13). Calcination at 1000 F. for16 hours alone is seen to produce some small removal of alumina from theacid faujasite as indicated by the somewhat smaller unit cell sizeproduced (Experiment 1). However, steaming alone at temperatures of 800F., 1000" F. and 1200 F. is more effective than calcination alone asevidenced by a greater degree of reduction in the unit cell size andadditionally by a superior retention of crystallinity in the product(Experiments 6, 8 and 10). The results of Experiment 9 indicate that thedegree of ammonium exchange is important in alumina extraction since asingle exchange with ammonium ions followed by steaming at 1000 F. for16 hours produced a material exhibiting a unit cell size which isvirtually unchanged from the starting material thereby indicating anabsence of effective alumina removal. It is further evident thatExperiments 5, 7, and 12, wherein the acid faujasite is treated with acalcination and/or steaming step prior to acid extraction yield aproduct having the lowest order of unit cell size while at the same timemaintaining or even enhancing the degree of crystallinity in the productmaterial. But, it is also clear that, by comparing Experiments 4 and 5,and 6 and 7, that the employment of the acid extraction step inconjunction with the heat treatment procedure is not absolutelyessential for the preparation of the high silica to alumina mole ratiocatalysts of the present invention.

This example shows the improvement in activity and selectivity incatalytic reactions exhibited by crystalline aluminosilicate zeolitemolecular sieves treated by the process of the present invention. Inthis example, a fanjasite treated as per Experiment 12 from Example 1was tested for cracking activity in a 95% silica-alumina matrix (13% A10 after steam deactivation at 1500 F. The results are tabulated below inTable VII and compared to a standard catalyst consisting of 5% regularH-faujasite in the same silica-alumina matrix and after the same 1500"F. steam deactivation.

TABLE VII [GOO-700 F. E. Texas G.O., 050 F., 2-minute cycle, Conversion]Untreated H faujasite Experiment No.12 taujasite Catalyst (l,500 F.steamed):

W./hr./w

to the better stability arising from the higher silica to alumina moleratio of this catalyst (about 15/1 versus about 5/1 in the untreatedfaujasite). The improved selectivity of the treated catalyst isevidenced by the lower carbon make and somewhat higher yield of gasolinefraction.

Example 3 This example illustrates the preparation of a new compositionof matter consisting of a pure silica faujasite, i.e., a crystallinematerial exhibiting the X-ray diffraction pattern of faujasite butcontaining no alumina tetrahedra and additionally no metal cations sincethe silica lattice is essentially electronically neutral. A goodcrystalline sodium faujasite having SiO /Al O ;6.0 is exchanged to theammonium form. Residual Na 0 content is 2.0% or less. This material issteamed at 1400 F. in one atm. steam for 24 hours. The resultingsteam-modified zeolite is extracted with 0.1 N HCl at C.; the amount ofacid should be sufiicient to give a final pH equal to 2 or less. Thewashed and dried product consists of a crystalline polysilicate havingan X-ray diffraction pattern of faujasite but which is essentially freeof A1 0 and Na O. The cell size of this polysilicate faujasite is about24.2 A. within experimental error).

Example 4 A sample of large-pore mordenite (Zeolon-Na supplied by NortonCompany) is exchanged to the NH.;-{- form by repeated treatments with10% NH NO solution of F. The washed and dried product is steamed at 1400F., 1 atm. steam for 24 hours. The steam-modified zeolite is extractedwith 0.1 N HCl until the pH is less than 2.0. The washed and driedproduct consists of a crystalline polysilicate having an X-raydiifraction pattern of mordenite but which is essentially free of A1 0and Na O. The unit cell dimensions of the polysilicate mordenite Withinexperimental error are about the following a =17.98 A.; b =20.33 A.; c=7.46 A. (orthorhombic unit cell).

Example 5 A sample of synthetic (K, Na)-erionite having SiO /Al O =6.0was exchanged five times with 10% NH NO solution at 180 F. The productcontained 0.1% Na O and 5.0% K 0. This material was steamed at 1000 F.in 1 atm. steam for 16 hours then extracted with the acid form of acation exchange resin as described in Example 1. The washed and driedproduct gave SiO /Al O 20 by analysis, no detectable residual Na O andless than 1% residual K 0. The product shows 43% of the original X-raycrystallinity but the cell size 0 for the hexagonal unit cell haddecreased from 13.20 to 13.13 A.

13 Example 6 The procedure of Example 5 is utilized to produce acrystalline polysilicate having the X-ray diffraction pattern oferionite which is essentially free of A1 Na O and K 0. This materialexhibits unit cell dimensions which within experimental error are asfollows: a =13.09 A.; 0 :14.92 A. (hexagonal unit cell).

It is evident that the process of the present invention can be extendedso as to produce crystalline zeolites having extremely high silica toalumina mole ratios and which have been further modified by impregnationwith selected metal ions or compounds so as to produce specificallydesirable compounds as catalysts for selected reactions. For example, itis within the scope of the present invention to impregnate the productof the present inventive process with such metal cations as silver,calcium, beryllium, barium, magnesium, zinc, aluminum, titanium,zirconium, chromium, iron, manganese, cerium, the rare earth metals,platinum, palladium, and other metals such as listed in column 5, lines26-29 and lines 56-63, mixtures thereof. It is also possible to formcomposites of the high silica to alumina mole ratio crystallinemolecular sieves with catalytically active compounds of molybdenum,tungsten, palladium, platinum, etc. by impregnation. Other variations inthe process and products of the present invent-ion will be evident toone skilled in the art.

What is claimed is:

1. A hydrocarbon conversion process which comprises contacting ahydrocarbon feed under conversion conditions with a crystallinealuminosilicate zeolite of the molecular sieve type, which sieveinitially has a silica-to alumina mole ratio greater than 3-5, and whichmolecular sieve is additionally at least partially in its ammonium orhydrogen form, and which sieve further has been activated by treatmentat a temperature in the range of about 80 0 to 1500" F. in an atmospherecontaining at least 2% water, for a period of time suflicient to effectremoval of sufiicient alumina tetrahedra from said molecular sievecrystal lattice such that the silica-to-alumina mole ratio of saidmolecular sieve is increased substantially above its initial value, andwherein subsequent to said activation, said molecular sieve is baseexchanged with cations selected from the group consisting of ammoniumions and metal cations selected from Groups II-A, VHI and the rare earthmetals, and mixtures thereof.

2. The process of claim 1 wherein said heat treatment atmospherecontains at least 5% water.

3. The process of claim 1 wherein said heat treatment atmospherecontains at least 25% water.

4. The process of claim 1 wherein sufficient alumina tetrahedra areremoved from said molecular sieve such that the silicato-alumina moleratio of said molecular sieve is increased to a value greater than 5-10.

5. The process of claim 1 wherein sufficient alumina tetrahedra areremoved from said molecular sieve such that the silica-to-alumina moleratio of said molecular sieve is increased to a value greater than about20 6. The process of claim 1 wherein sufiicient alumina tetrahedra areremoved from said molecular sieve such that the silica-to-alumina ratioof said molecular sieve is increased to a value greater than about 50.

7. The process of claim 1 wherein said activation is carried out at atemperature in the range of about 1000" to 1200 F.

8. The process of claim 1 wherein said base exchange step is carried outsuch that the final zeolite product has an alkali metal content belowabout 0.5 Wt. percent.

9. A hydrocracking process which comprises contacting a hydrocarbon feedin the presence of hydrogen under hydrocracking conditions with acrystalline aluminosilicate zeolite of the molecular sieve typeinitially having a silica-to-alumina mole ratio greater than 3-5, whichmolecular sieve is a least partially in its ammonium or hydrogen formand which sieve further has been activated by treatment with steam at atemperature in the range of about 1000 to 1200" F. and a pressure of atleast about 10 p.s.i.a. for a period of time sufficient to effectremoval of suflicient alumina tetrahedra from said molecular sievecrystal lattice such that the silica-to-alumina mole ratio of saidmolecular sieve is increased substantially above its initial value andwherein said sieve has impregnated thereon subsequent to said steamtreatment a minor amount of a hydrogenation component selected from thegroup consisting of Groups II-B through VII-B and Group VII of thePeriodic Table.

10. The process of claim 9 wherein, subsequent to said steam treatmentstep, said molecular sieve is base exchanged with cations selected fromthe group consisting of ammonium ions and metal cations selected fromGroups II-A, VIII and the rare earth metals, and mixtures thereof, suchthat the final zeolite product has an alkali metal content below about0.5 wt. percent.

11. The process of claim 9 wherein sufficient alumina tetrahedra areremoved from said molecular sieve such that the silica-to-alumina ratioof said molecular sieve is increased to a value greater than 5-10.

12. The process of claim 9 wherein suflicient alumina tetrahedra areremoved from said molecular sieve such that the silica-to-alumina ratioof said molecular sieve is increased to a value greater than 20.

13. The process of claim 9 wherein sufficient alumina tetrahedra areremoved from said molecular sieve such that the silica-to-alumina ratioof said molecular sieve is increased to a value greater than 5 0.

14. The process of claim 9 wherein the molecular sieve is wet aircalcined at a temperature in the range of about 650 to 1200 F. prior tosaid treatment with steam.

15. A method for increasing the silica/alumina mole ratio of acrystalline aluminosilicate zeolite which comprises (1) cationexchanging said zeolite in the alkali metal form with a cation selectedfrom the group consisting of hydrogen and hydrogen precursor ions, (2)contacting said zeolite with steam at a temperature in the range ofabout 1000 to 1200- F., and (3) cation exchanging said steam treatedzeolite with a cation selected from the group consisting of ammoniumions, metals of Groups I-I-A, I-B to VII-B and VIII of the PeriodicTable and the rare earth metals with atomic numbers 57 to 71.

16. The method of claim 15 wherein the final zeolite product has analkali metal content below about 0.5 wt. percent.

17. The method of claim 15 wherein the final zeolite product has analkali metal content below about 0.2 wt. percent.

18. The method of claim 15 wherein the initial crystallinealuminosilicate zeolite is selected from the group consisting ofmordenite, faujasite, chabazite, gmelinite, analcite, erionite and theirsynthetic counterparts.

19. The method of claim 15 wherein the cation exchange of step (3) iscarried out with a cation selected from the group consisting of metalsof Groups II-A, VIII and the rare earths.

20. The process of claim 1 wherein said heat treatment atmospherecontains steam.

References Cited UNITED STATES PATENTS 3,493,519 2/1970 Karr et a1.252-455 DELBERT E. GANTZ, Primary Examiner R. M. BRUSKIN, AssistantExaminer US. Cl. X.R.

